Spiral pipe is used in a variety of duct work applications. Spiral pipe is typically manufactured from galvanized steel, and is available in a wide variety of diameters, ranging from 3-inches to 80-inches. Similarly, spiral pipe is available in a wide wall thickness, ranging from 26-gauge up through 16-gauge. Lastly, spiral pipe may come in a variety of lengths, ranging from 1-foot to 20-feet, with 10-feet lengths being standard.
Spiral pipe is made by forming a coil of metal into a rigid steal tube with a four-ply spiral lock seam. Though it is common in the art to refer to this type of pipe as “spiral pipe” pipe, the seam of the pipe extends helically along the length of the pipe. Forming the spiral pipe in this way results in the pipe having a resistance to crushing approximately 2½times that of a longitudinally box seamed or longitudinally welded pipe. In addition, the spiral pipe has a smooth interior for low friction loss because the grooved seam is entirely on the outside. This low friction loss inside the spiral pipe allows the air to flow smoothly or “tumble” down the tube, increasing the efficiency of air flow through the spiral pipe.
Pipe-to-pipe connections are typically made using a fitting size coupling that slips inside the mating pipe sections. A stop bead runs around the middle of the coupling to center the coupling between the two pipe sections. The coupling is then secured by installing sheet metal screws through the outer shell of the duct a half inch from the stop bead. This method is time-consuming, increases the labor lost, and requires the tools and space necessary to allow the coupling to be attached to the spiral pipes. Further, the resulting connection created at the coupling may reduce the efficiency of the air flow through the spiral pipes. Specifically, the air does not flow efficiently through the pipes due to the coupling, the screws attaching the coupling to the spiral pipes, and any imperfections in the fit between the coupling and the two lengths of spiral pipe.
As an alternative to a coupling inserted between two pipes, it is possible to fit two lengths of pipe together using a flange integrally formed on the end of each pipe. However, it has proven especially difficult to manufacture spiral pipe having an integrated flange at the end of the spiral pipe. A major challenge in forming a flange at the end of a spiral pipe is the four-ply seam which extends helically along the length of the pipe. It is difficult to bend the four-ply seam area of the spiral pipe to form the flange without damaging the spiral pipe. Often, the spiral pipe will break or crimp when attempting to form a flange at the location of the four-ply spiral seam.
Thus, there is a need in the art for a spiral pipe having an integrated flange located at the end of the length of pipe. Similarly, there is a need in the art for a method of manufacturing a spiral pipe having an integrated flange.